Large, fast-sinking carcasses (food-falls) are an important source of nutrition to deepsea benthic communities. In 2007 and 2009, mass depositions of the salp Thetys vagina were observed on the Tasman Sea floor between 200 and 2500 m depth, where benthic crustaceans were observed feeding on them. Analysis of a long-term (1981 to 2011) trawl survey database determined that salp biomass (wet weight, WW) in the eastern Tasman Sea regularly exceeds 100 t km −3 yr −1 , with biomasses as high as 734 t km −3 recorded in a single trawl. With fast sinking rates, salp fluxes to the seafloor occur year-round. Salps, like jellyfish, have been considered to be of low nutritional value; however, biochemical analyses revealed that T. vagina has a carbon (31% dry weight, DW) and energy (11.00 kJ g −1 DW) content more similar to that of phytoplankton blooms, copepods and fish than to that of jellyfish, with which they are often grouped. The deposition of the mean yearly biomass (4.81 t km −2 WW) of salps recorded from the trawl database in the Tasman Sea represents a 330% increase to the carbon input normally estimated for this region. Given their abundance, rapid export to the seabed and high nutritional value, salp carcasses are likely to be a significant input of carbon to benthic food webs, which, until now, has been largely overlooked.

During the BP Deepwater Horizon (DWH) oil spill in 2010, 319 live oiled sea turtles were rescued and admitted to rehabilitation centers for decontamination and veterinary care. Most turtles were small, surface-pelagic juveniles that were collected from oiled habitat distant from shore. Serial hematology, plasma biochemistry, and blood gas analyses were reviewed to characterize abnormalities relative to observed degree of oiling. Clinicopathological abnormalities upon admission indicated acute, nonspecific metabolic and osmoregulatory derangements that were attributable to a combination of events including stress, exertion, physical exhaustion, and dehydration related to oiling, capture, and transport. Specific toxicological effects reported in other taxa were not observed. Initial point-of-care blood data from one rescue center were evaluated using clinical assessment of physiological status for all turtles of all species with available data for pH, pCO 2 , sodium, and potassium. In addition, a prognostic model that was specifically developed for cold-stunned Kemp's ridley sea turtles Lepidochelys kempii was applied to oiled Kemp's ridley turtles from one center. Thirty-six percent of oiled turtles were identified as physiologically de ranged based on a clinical assessment of their physiological status, and 25% of oiled Kemp's ridley sea turtles exceeded the mortality risk threshold of the prognostic model. These results indicate that the physiological derangements in these animals were relatively severe and clinically relevant. Based on observations during the DWH spill, adverse physiological effects in sea turtles may be an important consequence of stress, exertion, physical exhaustion, and dehydration secondary to oiling, capture, and transport.

Summary1. Within-individual plasticity (acclimation) counteracts potentially negative physiological effects resulting from environmental changes and thereby maintains fitness across a broad range of environments. The capacity for the acclimation of individuals may therefore determine the persistence of populations in variable environments. 2. We determined phylogenetic relationships by Amplified Fragment Length Polymorphism (AFLP) analysis of six populations of mosquitofish (Gambusia holbrooki) from coastal and mountain environments and compared their capacity for thermal acclimation to test the hypotheses that acclimation capacity is greater in more seasonal environments with less diurnal variability, that acclimation is genetically constrained and that demographic processes determine acclimation capacity. 3. We show that populations are divided into distinct genetic lineages and that populations within lineages have distinct genetic identities. There were significant differences in the capacity for acclimation between traits (swimming performance, citrate synthase and lactate dehydrogenase activities), between lineages and between populations within lineages. 4. We rejected the hypothesis that climatic conditions (coastal vs. mountain) determined the capacity for acclimation, but accepted the hypotheses that demographic processes and genetic constraint influenced thermal acclimation. 5. The importance of our data lies in proof of concept that there can be substantial variation in thermal plasticity between populations within species. Similar responses are likely to be found in other species that comprise structured populations. Many predictions of the impact of climate change on biodiversity assume a species-specific response to changing environments. Based on our results, we argue that this resolution can be too coarse and that analysis of the impacts of climate change and other environmental variability should be resolved to a population level.

No abstract

The nature of surfaces has been shown to have significant effects on the settlement of marine organisms. However, the few studies on the effect of natural rock surfaces on barnacle settlement have produced conflicting results. Here the settlement of Balanus balanoides (L.) cyprids on a variety of natural rock-types is investigated in situ in the absence of strong colour cues. The potential effect of surface texture was minimised as only 5 of the 15 examined rocks showed significant differences in surface rugosity. Significant differences in settlement preferences between rock types were observed independent of any potential effect of surface rugosity or colour cues which were found to have no effect on settlement. Slate was the most attractive rock-type followed by quartz and marble. Millstone grit sandstone and granitic gneiss were the least attractive and showed significant differences from slate, quartz and marble but not from all other rock-types. It is proposed that these differences are due either individually or in combination to the ability of a particular rock-type to sequest/partition solutes, and the scale of the physio-chemical heterogeneity of the rock type.

The bivalve mollusc Corbula gibba (Olivi) is often regarded as an invasive weed species that forms monospecific stands in organically enriched hypoxic habitats. However, despite its status as a potential menace, surprisingly little is known about its basic biology, including its dispersal capacity. Measurement of the respiration rate of C. gibba revealed a respiratory demand of 3.12 µl O 2 h -1 and a respiratory quotient of 0.61, which suggests that C. gibba adopts a conservationist rather than exploitative mode of life. Examination of the hypoxic tolerance of C. gibba determined that adults could survive for > 34 d (LT 50 ≥ 34 d) and juveniles for > 30 d (LT 50 = 14 d), indicating that this species is well adapted to living in low oxygen habitats. Unusually, adults under hypoxia had a greater survival rate than control adults in normoxic conditions. Investigation of the salinity tolerance of C. gibba revealed that it could readily survive for 2 d at 0 to 16 psu, with increasing mortality for up to 10 d. In brackish seawater, survival was indistinguishable from that in normal seawater. Examination of the population genetics of 6 different populations of C. gibba separated over various spatial scales, using RAPD PCR methodology, determined that all populations were genetically distinct from each other, including populations separated by as little 5 km, although this may in part be due to the influence of a localised front. This suggests that the larval longevity and dispersal capacity of C. gibba is much less than has been previously considered. In light of all the results, it is concluded that instead of being an insidious pest species, C. gibba is more likely to be an inferior competitor, present in background numbers in normoxic habitats, and only becomes dominant when a system becomes hypoxic, thereby removing competitors and allowing C. gibba to flourish in the habitat to which it is adapted.

No abstract

Distributions of stable isotopes have been used to infer an organism's trophic niche width, the ‘isotopic niche’, and examine resource partitioning. Spatial variation in the isotopic composition of prey may however confound the interpretation of isotopic signatures especially when foragers exploit resources across numerous locations. In this study the isotopic compositions from marine assemblages are modelled to determine the role of variation in the signature of prey items and the effect of dietary breadth and foraging strategies on predator signatures. Outputs from the models reveal that isotopic niche widths can be greater for populations of dietary specialists rather than for generalists, which contravenes what is generally accepted in the literature. When a range of different mixing models are applied to determine if the conversion from δ to p-space can be used to improve model accuracy, predator signature variation is increased rather than model precision. Furthermore the mixing models applied failed to correctly identify dietary specialists and/or to accurately estimate diet contributions that may identify resource partitioning. The results presented illustrate the need to collect sufficiently large sample sizes, in excess of what is collected under most current studies, across the complete distribution of a species and its prey, before attempts to use stable isotopes to make inferences about niche width can be made.